U.S. Pat. No. 4,082,962 (Burgsdorf et al.), U.S. Pat. No. 4,085,338 (Genrikh et al.) and U.S. Pat. No. 4,126,792 (Genrikh et al.) describe apparatus and systems for de-icing high voltage grids and power transmission lines by flowing a continuous current obtained using a rectifier circuit. The lines to be de-iced must be temporarily put out of service in order to perform the de-icing operation. In certain cases, supplementary devices must be added to the grid before being able to perform a de-icing operation, such a device being for example a circuit for grounding the lines to be de-iced.